Reasons I mostly use TF2
1) I'm not much of a HL2 fan. I can appreciate it for what it is, but that's just an FPS. It just doesn't do it for me. It's not the best game i've played nor does it even come close. TF2 is much better.
2) HL2 maintains a serious atmosphere so it's hard to make fun of it without going crazy about it. TF2 get's most of it's fun from the humor the game provides.
3) I have yet to port the files for L4D2 to my GM folder, also the fact that I don't wish to.

If you're going to pock fun of us for using TF2 mostly, just remember, it's GMOD construct, not TF2 construct. Any pic is welcome here, if it's made in Gmod.